The works of Francis Bacon, lord chancellor of England.

CENT. II. NATURAL HISTORY. 27
principal cause of violent motion, though un- as in blowing of the fire by bellows; greater
observed, passeth without sound; for that sound than if the bellows should blow upon the air
that is heard sometimes is produced only by the itself. And so likewise flame percussing the air
breaking of the air, and not by the impulsion of strongly, as when flame suddenly taketh and
the parts. So it is manifest, that where the openeth, giveth a noise; so great flames, while
anterior body giveth way, as fast as the posterior the one impelleth the other, give a bellowing
cometh on, it maketh no noise, be the motion sound.
never so great or swift. 120. There is a conceit runneth abroad, that
116. Air open, and at large maketh no noise, there should be a white powder, which will disexcept it be sharply percussed; as in the sound charge a piece without noise; which is a dangerous
of a string, where air is percussed by a hard and experiment if it should be true: for it may cause;tiff body, and with a sharp loose: for if the secret murders. But it seemeth to me impossible;
string be not strained, it maketh no noise. But for if the air pent be driven forth, and strike the
where the air is pent and straitened, there breath air open, it will certainly make a noise. As for
or other blowing, which carry but a gentle per- the white powder, if any such thing be, that may
cussion, suffice to create sound; as in pipes and extinguish or dead the noise, it is like to be a
wind-instruments. But then you must note, that mixture of petre and sulphur, without coal. For
in recorders, which go with a gentle breath, the petre alone will not take fire. And if any man
concave of the pipe, were it not for the ftipple that think that the sound may be extinguished or
straiteneth the air, much more than the simple deaded by discharging the pent air, before it
concave, would yield no sound. For as for other cometh to the mouth of the piece and to the open
wind-instruments, they require a forcible breath; air, that is not probable; for it will make more
as trumpets, cornets, hunters' horns, &c., which divided sounds: as if you should make a crossappeareth by the blown cheeks of him that barrel hollow through the barrel of a piece, it
windeth them. Organs also are blown with a may be it would give several sounds, both at the
strong wind by the bellows. And note again, nose, and at the sides. But I conceive, that if it
that some kind of wind-instrunments are blown at were possible to bring to pass, that there should
a small hole in the side, which straiteneth the be no air pent at the mouth of the piece, the
breath at the first entrance; the rather, in respect bullet might fly with small or no noise. For
of the traverse and stop above the hole, which first, it is certain, there is no noise in the percusperformeth the fipple's part; as it is seen in flutes sion of the flame upon the bullet. Next, the
and fifes, which will not give sound by a blast at bullet, in piercing through the air, maketh no
the end, as recorders, &c., do. Likewise in all noise as hath been said. And then, if there be
whistling, you contract the mouth; and to make no pent air that striketh upon open air, there is
it more sharp, men sometimes use their finger. no cause of noise; and yet the flying of the
But in open air, if you throw a stone or a dart, bullet will not be stayed. For that motion, as
they give no sound; no more do bullets, except hath been oft said, is in the parts of the bullet,
they happen to be a little hollowed in the casting; and not in the air. So as trial must be made by
which hollowness penneth the air: nor yet arrows, taking some small concave of metal, no more
except they be rufled in their feathers, which than you mean to fill with powder, and laying
likewise penneth the air. As for small whistles the bullet in the mouth of it, half out into the
or shepherds' oaten pipes, they give a sound be- open air.
cause of their extreme slenderness, whereby the 121. I heard it affirmed by a man that was a
air is more pent than in a wider pipe. Again, great dealer in secrets, he was but vain, that there
the voices of men and living creatures pass was a conspiracy, which himself hindered, to
through the throat, which penneth the breath. have killed QueenMary, sisterto Queen Elizabeth,
As for the Jews-harp, it is a sharp percussion; by a burning-glass, when she walked in St.
and besides, hath the advantage of penning the James's park, from the leads of the house. But
air in the mouth. thus much, no doubt, is true; that if burning117. Solid bodies, if they be very softly per- glasses could be brought to a great strength, as
cussed, give no sound; as when a man treadeth they talk generally of burning-glasses that are
very softly upon boards. So chests or doors in able to burn a navy, the percussion of the air alone,
fair weather, when they open easily, give no by such a burning-glass, would make no noise;
sound. And cart-wheels squeak not when they rto more than is found in coruscations and lightare liquored. nings without thunders.
118.'The flame of tapers or candles, though it 122. I suppose, that impression of the air with
be a swift motion and breaketh the air, yet passeth sounds asketh a time to be conveyed to the sense,
without sound. Air in ovens, though, no doubt, as well as the impressing of species visible; or
it doth, as it were, boil and dilate itself, and is else they will not be heard. And therefore, as
repercussed; yet it is without noise. j the bullet moveth so swift that it is invisible; soe
119. Flame percussed by air giveth a noise; | the same swiftness of motion maketh it inaudible;